1. Field of the Invention
The present invention relates to a water detector probe and more particularly to a probe used for determining the presence of water in the sump of a monitor vessel or of a filter/separator.
2. Description of the Prior Art
The presence of water in a sump of a filter/separator indicates that the jet fuel or other hydrocarbon products contained in the sump have been contaminated with water. Typically, when a maximum allowable level of water is sensed, the pumping of the contaminated material is stopped. Presently, there are two types of automatic systems which are operative to stop fuel flow when water is sensed.
One system incorporates a float that tends to float on the water/fuel interface. The other system is one that employs an electrical conductor which senses a maximum allowable level of water in the sump by electrical conductivity. Since this latter system requires very low electrical power, it is referred to as being intrinsically safe. In other words, should the system create an electrical spark, the system energy is insufficient to ignite an explosive fuel/air mixture.
The present invention involves a probe having special features for periodic testing of the electrical sensing system. There are presently two types of periodic testing systems. One of the systems employs a technique wherein water is injected into the sump of a fuel/separator. Such a system has been found to be undesirable because there could be instances where too much water injected into the system could possibly result in contaminated fuel being pumped into an aircraft. The other electrical system uses a periodic testing technique where water is injected into the internal cavity of the probe such that the water is caused to contact the portion of the electrode on the “air” side, as distinguished from the “fuel” side. If the injected water is also in contact with the body of the probe, continuity is established and a current is caused to flow to activate an intrinsically safe relay in an isolated electrical control box. Then current is caused to flow in an associated circuit to produce a signal to either stop the pumping system or to actuate a valve to prevent any flow of contaminated fuel to an associated aircraft.
One of the problems with the last mentioned system is that a false signal can occur during the test in the event the fuel side of the probe has been contaminated with deposits or has corroded. In either event, the conducting surface of the probe is prevented from being wetted by water in the sump.
It is an object of the present invention to produce a water detector probe which can be wetted with water on the fuel side of the probe to enable the detection of very small quantities of water so as to create no subsequent hazard to an aircraft engine.